Zhang Shixiong, Hemesath Eric R, Perea Daniel E, Wijaya Edy, Lensch-Falk Jessica L, Lauhon Lincoln J
Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA.
Nano Lett. 2009 Sep;9(9):3268-74. doi: 10.1021/nl901548u.
We quantitatively examine the relative influence of bulk impurities and surface states on the electrical properties of Ge nanowires with and without phosphorus (P) doping. The unintentional impurity concentration in nominally undoped Ge nanowires is less than 2 x 10(17) cm(-3) as determined by atom probe tomography. Surprisingly, P doping of approximately 10(18) cm(-3) reduces the nanowire conductivity by 2 orders of magnitude. By modeling the contributions of dopants, impurities, and surface states, we confirm that the conductivity of nominally undoped Ge nanowires is mainly due to surface state induced hole accumulation rather than impurities introduced by catalyst. In P-doped nanowires, the surface states accept the electrons generated by the P dopants, reducing the conductivity and leading to ambipolar behavior. In contrast, intentional surface-doping results in a high conductivity and recovery of n-type characteristics.
我们定量研究了体杂质和表面态对含磷（P）和不含磷的锗纳米线电学性质的相对影响。通过原子探针断层扫描确定，名义上未掺杂的锗纳米线中的无意杂质浓度小于2×10¹⁷ cm⁻³。令人惊讶的是，约10¹⁸ cm⁻³的P掺杂使纳米线的电导率降低了2个数量级。通过对掺杂剂、杂质和表面态的贡献进行建模，我们证实名义上未掺杂的锗纳米线的电导率主要是由于表面态诱导的空穴积累，而不是催化剂引入的杂质。在P掺杂的纳米线中，表面态接受P掺杂剂产生的电子，降低了电导率并导致双极行为。相比之下，有意进行表面掺杂会导致高电导率并恢复n型特性。
